Apparatus for separating hosiery articles

ABSTRACT

A machine attachment for separating tubular knitted articles knitted in succession and connected each to the next succeeding one by a frangible joining thread, in accordance with which the fabric is gripped above and below a separation line and between the positions of gripping the fabric is deflected laterally by a pusher device until the joining thread is fractured and the leading article separated from the next succeeding one, the separated article being subsequently drawn away through a discharge tube . The pusher device is conveniently formed as part of a short tube through which the fabric from the knitting machine passes, which tube is slidable laterally between upper and lower openings for passage of the fabric, which openings have flaps to close them and provide for the gripping of the fabric.

United States Patent [1 1 Perkins APPARATUS FOR SEPARATING I-IOSIERY ARTICLES Dec. 18, 1973 FOREIGN PATENTS OR APPLICATIONS 703,237 2/1954 Great Britain 225/105 Primary Examiner-Robert R. Mackey Attorney-Linton and Linton [57] ABSTRACT A machine attachment for separating tubular knitted articles knitted in succession and connected each to the next succeeding one by a frangible joining thread, in accordance with which the fabric is gripped above and below a separation line and between the positions of gripping the fabric is deflected. laterally by a pusher device until the joining thread is fractured and the leading article separated from the next succeeding one, the separated article being subsequently drawn away through a discharge tube The pusher device is conveniently formed as part of a short tube through which the fabric from the knitting machine passes, which tube is slidable laterally between upper and lower openings for passage of the fabric, which openings have flaps to close them and provide for the gripping of the fabric.

8 Claims, 6 Drawing Figures PATENTEU 3W5 3,779,046

sum 1 OF 6 FIGI.

INVENT'GQ CHARLES WILL/N PERKINS "By 05%: WM

RTTORNEYS PATENTEDIJEEI 8W5 sum m 6 3179,0425

, M vrwroR CH/IRLES WILLIN PERKINS PATENTEUUECI 8 1975 SHEET 5 OF 6 :INYEIYTOR CHARLES Wit-LIN PERKINS 5 Mafia Q 'TORNEYS APPARATUS FOR SEPARATING HOSIERY ARTICLES This invention is for improvements in or relating to the knitting of tubular fabric and is concerned more particularly with the separation of a succession of tubular knitted articles knitted end to end in continuous tubular formwithout being pressed off from the needles. The invention has for an object to provide a comparatively simple and effective procedure and apparatus for separating individual articles from the continuous fabric for delivery singly in succession from the knitting machine.

In the production of some circularly knitted articles, for example half hose, it is a well-known procedure to knit a succession of the articles joined end to end in continuous tubular form without pressing off the product from the needles, successive articles being joined to the preceding ones by courses formed of a joining thread sometimes known as a draw thread, which courses are intended to be subsequently removed to separate-the articles from one another. Such joining courses are usually formed from a soluble yarn so that, after this has been severed to separate the articles, remaining parts of the joining courses can be subsequently dissolved out when the articles are subjected to dyeing and finishing treatment. The soluble yarn used for such joining courses is substantially weaker than a normal yarn used for knitting the articles. The invention seeks to provide a procedure and apparatus whereby the articles can be separated from one another by fracture of a joining thread of this kind in a simple and convenient way. i

In accordance with the invention there is provided a method of producing tubular knitted articles on a circular knitting machine according to which the articles are knitted in succession and connected to one another by a joining thread which. is weaker than the yarn used for forming the articles, and the articles are afterwards separated from one another by gripping the tubular fabric at positions offset opposite ways from the courses of joining thread separating a succeeding article from a preceding article and deflecting the fabric transversely between said gripping positions so as to exert a mechanical pull to rupture the joining thread. The joining thread is conveniently a soluble yarn as already referred to. This will readily rupture on having a sudden pull applied to it, and remaining parts of it can afterwards be dissolved away.

In practising the invention the mechanical pull is arranged to be applied to the fabric to separate the articles at a location on the machine at which the knitted fabric is being delivered below the take down rollers normally employed on a circular knitting machine organized to knit a succession of articles end to end. The manner of gripping the fabric at the said gripping position is conveniently such that the pull exerted to separate the fabric, which is conveniently exerted by a movable deflecting member, severs to enhance the holding action of the gripping means. It is advantageous to subject the fabric to air flow or suction action firstly to draw it taut between the gripping positions before it is gripped and afterwards to discharge the separated article after it has been released by the gripping means.

In a convenient procedure the action of separating each article after it has passed below the take down rollers is initiated at appropriate times by patterning means (e.g., a chain on the machine) and is controlled sequentially to cause the fabric to be drawn taut and then gripped as aforesaid, and then deflected laterally between the gripping positions to fracture a joining thread, following which the gripping of the fabric at the lower position is first released and the severed article is discharged. Such discharge may occur during return movement of a fabric deflecting member as aforesaid by release of the fabric at the lower gripping level, gripping of the fabric at the upper level being released at the conclusion of said return movement to allow the following fabric to pass downwardly. The parts of the apparatus by which these actions are performed are appropriately inter-related to perform automatically the required cycle of movements for gripping the fabric, separating an article therefrom and discharging it, and then resetting the parts for the next separating operation, in response to each actuation by'the patterning means aforesaid.

The invention further provides apparatus for use with a circular knitting machine for separating articles knitted in succession in continuous tubular form, comprising means for gripping the tubular knitted fabric at positions above and below a point at which separation is required, a deflecting member movable transversely between the upper and lower gripping means, means for actuating the gripping means at appropriate times for gripping and releasing fabric, and means for actuating the deflecting member while the fabric is gripped by the gripping means to deflect and stress the fabric so as to fracture a joiningthread at the required point of separation. Conveniently, the gripping means are so organized that the pull exerted on the fabric between them tends to cause both of the gripping means to hold the fabric more firmly. The apparatus is conveniently constructed as a unit capable of being fitted to an existing knitting machine at a position below the take down rollers.

In a convenient arrangement the deflecting member (herein sometimes referred to for convenience as the pusher) forms part of a tubelike assembly being a movable upper part of a fabric discharge tube to be positioned below take down rollers of the machine which assembly is bodily movable, transversely so that the knitted fabric is deflected by engagement with the pusher. This assembly may be slidably mounted in a box-like framework having upper and lower walls and flaps fitted to openings in such walls in the line of the normal discharge of the knitted fabric, the flap of the upper wall being hinged to swing upwardly and the flap of the lower wall hinged to swing downwardly to their open positions and both being spring urged to their closed positions. The. flaps are conveniently interconnected with the pusher so that when the latter is withdrawn to bring its tubular assembly in line with the discharge tube the flaps are both held open to allow the fabric to pass freely through said openings and through the tube like assembly of the pusher, and when the pusher commences its operative stroke the flaps are caused to close on to the fabric and grip it against edge parts of the said openings. With an arrangement of flaps as just described they may be caused tobe opened against the action of their springs by a simple lever action actuated by the pusher.

The flaps may have their edges at the positions of engagement with the fabric slanted in the appropriate directions to promote the exertion of greater pressure on the fabric to grip it when it is deflected and tensioned by the pusher.

The pusher assembly may be operated by a pneumatic cylinder, which is conveniently double acting for movement of the pusher in the fabric deflecting and releasing directions, respectively, and a control valve associated with the cylinder may be provided for actuation by a suitable control member on the knitting machine, e.g. a link of a patterning chain. The supply of compressed air for operating the pneumatic cylinder of the pusher assembly may also be utilized for feeding a blast unit used to create suction in the lower part of the discharge tube below the separating apparatus. Such blast unit may be controlled to operate at appropriate times for drawing the fabric taut before being deflected by the pusher and for withdrawing an article on becoming separated. The blast unit may be actuated by a control operated by the movement of the pusher. Additionally it is advantageous to arrange for the bottom gripper flap to be opened to release the fabric immediately after the pusher has completed its operative stroke and this may be caused by an air cylinder acting on the operating leverage of the lower flap and conveniently supplied by exhaust air from the pusher operating cylinder.

When the pusher returns to its rest position alongside the normal line of take down of the knitted fabric there may be a tendency for the depending end of the tubular fabric hanging from the take down rollers of the machine) to become caught up behind the pusher instead of dropping into the tube of the pusher assembly. To avoid this tendency an air flow is promoted from a jet or jets at an appropriate position to blow the depending fabric oppositely to the return movement of the pusher and such jet or jets may also be fed by exhaust air from the pusher operating cylinder.

A convenient form of apparatus in accordance with the invention is shown by way of example in the accompanying drawings in which:

FIG. 1 is a front elevation view of separating apparatus adapted for mounting on a circular knitting machine for knitting socks;

FIG. 2 is a perspective view showing the separating apparatus applied to a circular knitting machine, certain parts only of the machine being shown and appearing less prominently than the separating apparatus;

FIG. 3 is a detail view corresponding to part of FIG. 1 showing on a somewhat enlarged scale the parts in one position;

FIG. 4 is a view corresponding to FIG. 3 showing the parts in a different position;

FIG. 5 is a plan view of parts shown in FIGS. 3 and 4, and

FIG. 6 is a diagram of a pneumatic control circuit.

In FIGS. 1 and 2 of the drawings there is shown at 10 and 11 parts of a fixed bracket and shelf of a circular knitting machine which support a stationary ring 12 in which is rotatably mounted an inner ring 13 carrying upstanding brackets 14 supporting the usual take-down rollers shown, diagrammatically at 15. From the mountings of the stationary ring 12 there is supported by bolts or studs 16 and 17. and spacers 18 and 19 a framework 20 having-'jcorner posts and top and bottom plates 2land 22. The frame provides a mounting for the movable pusher and has openings 23 and 24 in its top and bottom plates 21 and 22 which are aligned with the vertical line of delivery, indicated by the chain line 25, of tubular knitted socks joined end to end in continuous length. The openings 23 and 24 are also aligned with a discharge tube comprising a funnel shaped inlet 26 secured to the bottom of frame 20 and tubes 27 and 28 continuing therefrom to a discharge pipe 28a (FIG. 7

the arms of its U shape secured to the sides of the pusher head 30. Thereby the parts 30 and 31 together form an upper part of the discharge tube. The fabric engaging face 32 of the pusher head is of smooth contour and convex form as seen in elevation in FIG. 1, but concave as seen in plan (see FIG. 5) thereby forming a smooth saddle to engage the knitted fabric. The pusher head 30 is mounted on the piston rod 33 of a pneumatic cylinder 34 by which it is moved to the right as seen in FIG. 1 when required to separate a sock from the string of socks delivered from the take-down rollers 15. The rest or inoperative position of the pusher 30 is as shown in FIGS. 1 and 3 in which projections 35 and 36 on the pusher head 30 engage with elbow shaped levers 37 and 38 pivoted at 39 and 40 to the top and bottom plates 21 and 22 and having their other arms engaged with tags 41 and 42 on flaps 43 and 44 pivoted at 45 and 46 to the top and bottom plates 21 and 22. The flaps 43 and 44 co-operate with the openings 23 and 24 and in the position shown in FIGS. 1 and 3 are held open by the pusher 30 against the action of springs not shown) such as springs coiled around the pivotal axes 45 and 46 and engaging the flaps 43 and 44 to urge them to horizontal closed positions in which they extend across the openings 23 and 24. Their free edges 43a and 44a are somewhat slanted as shown to cooperate in the closed settings of the flaps with the bars 47 and 48.

Also shown in FIG. 1 in broken lines is a pipe 49 leading to two nozzles 50 one only of which can be seen) spaced apart at positions corresponding to the near and far sides of the pusher head 30, and a blast injector tube and nozzle shown in broken lines at 51 and 51a extending into the part 28 of the discharge tube to create suction therein so as to draw the knitted fabric downwardly and discharge a sock on separation from the remainder of the knitted tubular fabric.

The apparatus is shown in FIG. 2 as applied to a knitting machine of a type sold under the Registered Trade Mark KOMET. Thus machine legs are shown at and 71, a control chain sprocket at 72, a driving motor at 73 while a part of the control drum is seen at 74. The fixed bracket 10 and shelf 11 can also be seen, while the take down rollers are indicated at 15, being supported by the brackets 14 aforementioned. The framework 20 can also be seen more fully inFlG. 2 as well as its mounting on the studs or bolts 16 and 17 and spacers l8 and 19.

The pneumatic cylinder 34 is double acting and its operation can be understood by reference to the pneumatic circuit shown in FIG. 6. As shown in FIG. 6, ports 34a and 34b at the opposite ends of cylinder 34 are connected to a reversing controlvalve 52, the inlet port 52a of which receives compressed air from a main supply indicated at 53. The control valve 52 has an inlet port 52a, two exit ports 56 and 57 and two exhaust ports 58 and 64. A slidable plunger valve 52b in the reversing control valve 52 has a rest position in which valve ducts admit compressed air from the inlet port 52a to the exit port 56, and connect the exit port 57 to the exhaust port 64. The valve 52b may alternatively be slid to a reversing position by means of compressed air from the main supply 53 which passes through a con trol valve 54. An energizing button 55 of the control valve 54 is arranged to be operated at an appropriate time during each complete knitting cycle by a stud on a pattern chain on sprocket 72) of the knitting machine in known manner, being a time when a completed sock hangs down partly into the discharge funnel 26 with the joining thread which connects it to the next succeeding sock in the string positioned between the openings 23 and 24. The button 55 when operated opens the control valve 54 to actuate the reversing control valve 52 to its reversing setting in which other ducts is the plunger valve 52b divert air from the main supply 53 to exit port 57 of the valve 52 and connect exit port 56 to exhaust at 58. Thus compressed air is supplied to port 34a of cylinder 34 and port 34b of said cylinder is connected to exhaust through port 56 and outlet 58. Also connected to the ports 56 and 57 of valve 52 is an air blast control valve 59 having two inlets 60 and 61, of which the inlet 60 is normally connected to an outlet 62 while the inlet 61 is shut off from outlet 62 and can be connected thereto in place of the inlet 60 by depression of a plunger 63. The outlet 62 is connected through pipe 51 to the air blast nozzle 51a. The exhaust outlet 64 of valve52 is connected through piping 65 and66 to a pneumatic cylinder 67 having a piston 67a therein adapted to bear against the bottom elbow shaped lever 38 on supply of air from the exhaust port 64 to the cylinder 67' so that when the cylinder 67 is energized the lever 38 is operated to open the bottom flap 44 irrespective of the position of the pusher 30.

On one of the guide rods 29 is mounted a tripping ring 75, which is freely slidable on the said guide rod. Lateral sliding movement of the tripping ring 75 on the said guide rod 29 is limited in one direction by the mounting collar 76 mounting the pusher head 30 on the said guide rod 29, and in the other direction by a projecting piece 77 projecting laterally from the pusher head 30 and having a bore therethrough for receiving the said guide rod 29..

The operation of the apparatus will now be described. In the rest position of the pusher 30 the tripping ring 75 is in the position shown in FIG. 3. In this position it maintains depressed the plunger 63 of the air blast control valve 59 so as to shut off the inlet 60 from the outlet 62 and connect the inlet 61 to the outlet 62.

During normal knitting of a sock on the knitting machine the air supply 53 is connected by the control valve 52 via the outlet port 56 thereof to the inlet 60 of the air blast control valve 59. Thus there is no air blast at 51a and no suction applied to the knitted socks. The air supply 53 also maintains the pusher 30 in its left hand rest position as shown in FIGS. 1, 2 and 3. When a sock is ready to be separated from the string of socks being delivered by the knitting machine, a stud on the pattern chain will operate valve 54 to reverse the connection of the main air supply through the control valve 52 from the port 56 to the port 57 thereby causing the pusher 30 which was previously in its left hand end or rest position as shown in FIG. 3 to be moved to the right towards the position shown in FIG. 4. Because the plunger 63 is depressed as described above, the reversal of the control valve 52 also supplies compressed air to the blast nozzle 51a via the inlet 61 and outlet 62 of the air blast control valve 59. This creates a suction in the discharge tube 26, 27 to draw the sock down taut during initial movement of the pusher 30. It will be seen from FIG. 3 that the tripping ring 75 is not moved away from the plunger-depressing position shown until it is engaged by a collar 76 of the pusher 30. Before these two members engage, the projections 35 and 36 of the plunger 30 disengage the elbow shaped levers 37 and 38 to release the flaps 43 and 44. The flaps 43 and 44 are thus urged by their springs to move to the positions shown in FIG. 4 to trap the chain of socks while the air blast nozzle 51 a is still operative. The chain of socks is thus trapped and gripped under tension above and below the position of the joining thread between the two bottom-most socks.

On continued movement of the pusher 30 to the right the collar 76 will move the tripping ring to the right to release the plunger 63 and the'connection between the inlet 61 and the outlet 62 of the air blast control valve 59 will thus be interrupted. Thus the suction in the discharge tube 26, 27 will cease. The pusher 30 then deflects the fabric so as to stress it and as it proceeds towards the right hand limit of its travel shown in FIG. 4 the joining threads will be caused to burstand break away so that the bottom sock is freed from the next sock above it. As soon as the pusher 30 has reached the right hand limit of its travel the control chain on the machine will have moved on so that its stud which actuated the button 55 of valve 54 will! release said button and the setting of valve 52 will then be reversed by a return spring. Air is then supplied through ports 56 and 34b to the right hand end of cylinder 34 and exhausted from the left hand end through ports 57 and 34a and outlet 64 into the pipes 65 and 66.

The reversal of valve 52 will cause the pusher 30 to commence its return stroke towards the left and at the same time connect port of valve 59 to the main air supply causing air to flow through outlet 62 to blast nozzle 51a thereby creating suction in the delivery pipe 26, 27. Some of the exhaust air from the left hand end of cylinder 34 will at this stage energize cylinder 67 to raise the piston 67a therein to operate the lever 38 in the anticlockwise sense so asto open the bottom flap 44 and allow the separated sock to be drawn away immediately through the discharge tube 26, 27, 28. Such exhaust air will also be partly supplied through pipes and 49 to the nozzles 50 to create a. draught of air from left to right inside the upper part of casing 20. This causes the portion of tubular fabric which at this stage depends from the closed upper flap 43 to be blown towards the right of FIG. 1 and prevented from becoming trapped behind the pusher 30 as it moves to the left.

At the conclusion of the return movement of pusher 30, the upper flap 43 is opened by engagement of the projection 35 with the elbow shaped lever 37 and, the air currents from nozzles50 having then ceased, the next part of the tubular knitted fabric is allowed to drop down through the opening 23 into the space within the shield 31 and to the right of pusher 30. Return movement of the pusher 30 to its rest position also causes the tripping ring 75, engaged on the return stroke of the pusher 30 by the projecting piece 77, to depress the plunger 63. Thus the air supply from the inlet 60 to the outlet 62 of the air blast control valve 59 is interrupted, and the suction in the discharge tube 26, 27 is discontinued. As soon as another knitting cycle has been completed the valve 54 will again be actuated by a stud on the control chain and the operations automatically repeated to separate and discharge the next sock.

It will be appreciated that the apparatus provided by the invention can be applied as a relatively compact unit to an existing knitting machine without impeding access to the working parts of the machine.

What I claim is:

1. Apparatus for separating articles knitted in succession end to end in the form of continuous tubular fabric with knitted courses of relatively weak joining thread interposed between the articles, comprising:

a. a supporting frame presenting a throughway with end openings for passage therethrough of the tubular fabric;

b. means for advancing the tubular fabric to bring the joining thread between adjacent articles into said throughway;

c. a fabric deflector movable across the throughway between the end openings thereof;

d. guiding means on said supporting frame to guide the deflector for movement between opposite extreme positions being fabric deflecting and nondeflecting positions;

e. first and second gripping means on the supporting frame positioned respectively at the opposite end openings of said throughway, each gripping means including a pivoted flap biassed to swing inwardly across the adjacent end of the throughway to exert on the fabric a gripping force that is increased by the pull of the fabric when deflected by the deflector, operating means to move the deflector opposite ways from one to the other of its extreme positions, and

g. mechanism actuated by the deflector to swing said pivoted flaps outwardly when the deflector is moved into its non-deflecting position and to free the flaps to swing inwardly during initial movement of the deflector when moved away from its nondeflecting position.

2. Apparatus according to claim 1 wherein the fabric deflector is part of a tube-like assembly and a fabric discharge tube is fixed to the supporting frame in registry with said throughway to receive separated articles from said deflector.

3. Apparatus according to claim 1 including a pneumatic cylinder for operating the deflector, a supply of compressed air, a control valve to control admission of air from the supply to the pneumatic cylinder and means for actuating said control valve.

4. Apparatus according to claim 3, including a discharge tube extending from said throughway, a blast unit for creating air discharge suction in said discharge tube, means for admitting air from said supply to the blast unit, and a control device actuated by said fabric deflector to cause operation of the blast unit at appropriate times for drawing the fabric taut and for with drawing a severed article.

5. Apparatus according to claim 3, having at least one air flow jet for acting on depending fabric at its entry into the deflecting apparatus to maintain said fabric in its proper path, and said control valve operating said air flow jet during return movement of the deflector.

6. Apparatus for separating articles knitted in succession end to end in the form of continuous tubular fabric with knitted courses of relatively weak joining thread interposed between the articles, comprising:

a. a box like supporting frame including upper and lower walls defining aligned openings;

b. an upright tube-like fabric deflector assembly, including a saddle-like pusher and a shield part, movably mounted between the upper and lower walls of the supporting frame;

0. guiding means on the supporting frame to guide the deflector assembly for movement between a non-deflecting position in line with said openings and a fully deflecting position offset laterally therefrom; I

d. upper and lower gripping means comprising flaps pivoted to said frame at said openings normally biased towards closed position to wedge the fabric against said upper and lower walls defining said openings;

e. deflector operating means to move the deflector assembly in each direction from one to the other of its non-deflecting and fully deflecting positions, and

f. lever mechanism acting on both of said gripping means and actuated by the deflector assembly to cause said gripping means to be open in the nondeflecting position of the deflector assembly and releasing said gripping means to closed position as the deflector assembly moves towards deflecting 

1. Apparatus for separating articles knitted in succession end to end in the form of continuous tubular fabric with knitted courses of relatively weak joining thread interposed between the articles, comprising: a. a supporting frame presenting a throughway with end openings for passage therethrough of the tubular fabric; b. means for advancing the tubular fabric to bring the joining thread between adjacent articles into said throughway; c. a fabric deflector movable across the throughway between the end openings thereof; d. guiding means on said supporting frame to guide the deflector for movement between opposite extreme positions being fabric deflecting and non-deflecting positions; e. first and second gripping means on the supporting frame positioned respectively at the opposite end openings of said throughway, each gripping means including a pivoted flap biassed to swing inwardly across the adjacent end of the throughway to exert on the fabric a gripping force that is increased by the pull of the fabric when deflected by the deflector, f. operating means to move the deflector opposite ways from one to the other of its extreme positions, and g. mechanism actuated by the deflector to swing said pivoted flaps outwardly when the deflector is moved into its nondeflecting position and to free the flaps to swing inwardly during initial movement of the deflector when moved away from its non-deflecting position.
 2. Apparatus according to claim 1 wherein the fabric deflector is part of a tube-like assembly and a fabric discharge tube is fixed to the supporting frame in registry with said throughway to receive separated articles from said deflector.
 3. Apparatus according to claim 1 including a pneumatic cylinder for operating the deflector, a supply of compressed air, a control valve to control admission of air from the supply to the pneumatic cylinder and means for actuating said control valve.
 4. Apparatus according to claim 3, including a discharge tube extending from said throughway, a blast unit for creating air discharge suction in said discharge tube, means for admitting air from said supply to the blast unit, and a control device actuated by said fabric deflector to cause operation of the blast unit at appropriate times for drawing the fabric taut and for withdrawing a severed article.
 5. Apparatus according to claim 3, having at least one air flow jet for acting on depending fabric at its entry into the deflecting apparatus to maintain said fabric in its proper path, and said control valve operating said air flow jet during return movement of the deflector.
 6. Apparatus for separating articles knitted in succession end to end in the form of continuous tubular fabric with knitted courses of relatively weak joining thread interposed between the articles, comprising: a. a box like supporting frame including upper and lower walls defining aligned openings; b. an upright tube-like fabric deflector assembly, including a saddle-like pusher and a shield part, movably mounted between the upper and lower walls of the supporting frame; c. guiding means on the supporting frame to guide the deflector assembly for movement between a non-deflecting position in line with said openings and a fully deflecting position offset laterally therefrom; d. upper and lower gripping means comprising flaps pivoted to said frame at said openings normally biased towards closed position to wedge the fabric against said upper and lower walls defining said openings; e. deflector operating means to move the deflector assembly in each direction from one to the other of its non-deflecting and fully deflecting positions, and f. lever mechanism acting on both of said gripping means and actuated by the deflector assembly to cause said gripping means to be open in the non-deflecting position of the deflector assembly and releasing said gripping means to closed position as the deflector assembly moves towards deflecting position.
 7. Apparatus according to claim 6, including pivotal mountings for said flaps whereby the flap of the upper wall is hinged to swing upwardly and the flap of the lower wall is hinged to swing downwardly.
 8. Apparatus according to claim 6 wherein the upper and lower gripping means have their edges at the positions of engagement with the fabric slanted to promote tighter gripping of the fabric when tensioned between the gripping means. 